Workpieces, including food products, are portioned or otherwise cut into smaller units or portions in accordance with customer needs. Food products are commonly portioned either into uniform or specific sizes, weights, thicknesses, or other specifications. Examples of commonly portioned food products include beef steaks served in restaurants, chicken filets packaged in frozen dinners or chicken patties sized and shaped to fit within specific bun configurations. Fish is likewise routinely portioned into filets or steaks.
Much of the portioning of workpieces, and in particular food products, is now carried out with the use of high-speed portioning machines. These machines use various scanning techniques to ascertain the size, shape, and other physical characteristics of the workpiece as it is being advanced on a moving conveyor. This information is analyzed with the aid of a computer to determine how to most efficiently portion the workpiece into optimum or desired sizes, weights, thicknesses, or other criteria being used. For example, the customer may desire chicken breast portions in two or more different weight(s) or sizes. The chicken breast is scanned as it moves on an infeed conveyor belt, and a determination is made through the use of the computer as to how best to portion the chicken breast to the specific weight(s) desired by the customer.
Portioning of workpieces can be performed by a cutting blade that swings across the conveyor system through a gap defined by the ends of two adjacent conveyors that advance and support the workpieces being portioned. Typically, the blade is attached to a servo motor, which spins the blade very quickly through the gap. The workpiece progresses forwardly on the conveyor belts across the gap, thereby advancing between successive blade revolutions. The blade may make approximately 20 to 30 cuts per second to provide controlled weight, thickness, or size portions, and consequently the timing of the blade passage through the conveyor belt gap must be very tightly controlled.
After the workpiece is scanned, it travels down the moving conveyor to the blade cutter. Using an encoder for monitoring the speed of the conveyor belt, the blade cutter is told by the computer when to cut through the workpiece so as to achieve portions of desired size, for example, desired weights or thicknesses. Thus, a delay occurs between the scanning of a workpiece and the cutting of the workpiece by the rotating cutting blade. This delay can be captured on an encoder count or position down the belt. The difference between the two encoder counts or positions of the workpiece is the “scan-to-cut” delay.
Errors can be caused in the “scan-to-cut” delay and thus the timing of the cutting of the workpiece may not be accurate. These errors can be due to variations in the portioning system operation and structure, as well as variations in the shape or configuration of the workpieces, and also due to the workpiece moving, or the workpiece otherwise being disturbed, before or during the cutting processing. All these variations can lead to the incorrect cutting of the workpiece. The present disclosure seeks to adjust for the foregoing variations by use of one or more calibration procedures, described below.